Following the unique preceding episodes, Sherlock takes another
distinct tonal turn with the finale of Series Three. This time,
we're heading into far more mature territory in terms of the
characterization and plotting, Steven Moffat's script taking the
viewer on a relentless rollercoaster of emotion and jaw dropping,
unexpected twists.

Make no mistake, this is arguably the darkest episode in the
series' history, going to places it has never trodden before. It is
emotionally devastating in ways completely different from The
Reichenbach Fall, while retaining a vein of tight, fierce humour
that relies explicitly upon character based incident and wordplay
that is also markedly different from the comedy that appears in The
Sign of Three, for example.

Paramount to the harder edge that defines His Last Vow is
Charles Augustus Magnussen, magnificently played by Lars Mikklesen.
Magnussen is a repellent, icy foe, a man so assured of his personal
power over others it gives him the justification to behave how he
likes. Completely different from Andrew Scott's volatile yet
insanely endearing Jim Moriarty, this is a luridly predatory,
genuinely skin crawling and frightening villain, someone who can
stand toe to toe with Benedict Cumberbatch's Sherlock Holmes and
yet, shockingly, dominate the room.

Without any specifics, the deployment of this striking new
antagonist induces a case - from the very start of the episode -
that causes the leading characters to be placed into situations
that we have never seen them enter before. Some we have potentially
been anticipating for a long time, others come out of nowhere. This
is not what some have cited as the 'fan service' that has appeared
in The Empty Hearse and The Sign of Three, more a logical
follow-through from previously established events and a fulfillment
of some possibly long held suspicions that coalesce into some
dramatic final closing scenes.

That said, His Last Vow continues the trend of this third run of
episodes in defying the expectations of an audience, a grand
adventure that raises the series to striking new heights. Steven
Moffat's script is magnificently Canon-laden, reverential asides
and cunning deviations running throughout in full effect, and it
also features plenty of further expansion and development. As some
of the events in The Sign of Three may have signposted, these are
now very much Steven Moffat and Mark Gatiss' versions of these
beloved characters, true yet not slavish to the originals written
by Sir Arthur Conan Doyle, and the character based aspects of the
narrative here flow from developments that we have already
seen.

Visually, this is another stunning episode, the use of location
in particular giving it a scale that eclipses the previous two
installments. Nick Hurran has been handed a gift of a screenplay
and certainly doesn't squander it, turning established rules on
their head at times and extrapolating others to new places. The Art
of Deduction, in particular, undergoes a striking and extended
renovation within the visual context of one showpiece, uniquely
dramatic sequence. David Arnold and Michael Price's score somehow
keeps getting larger and more expansive. It's impossible to wonder
how much higher and - dare we say it - operatic the pair could take
the themes they have developed across the three series of Sherlock
from here, but by now familiarity with the motifs they have created
is not a problem but an utter boon, not reliance but distinctive
calling cards that heighten the emotional response to what you are
seeing.

Yes, as we've already said, His Last Vow is an emotional
experience. To say anymore of the how's and why's that that is the
case would be churlish and wrong. Like The Empty Hearse, this is an
experience that should be Experienced, unsullied with prior
knowledge or spoilers of what is coming. Though there is one thing
we will say, to ensure your viewing of this barnstorming finale to
the third series of Sherlock is complete.

When the end credits start, do not turn off your television or
change the channel. Watch to the very close.